Below are the participant names per organization. The links on the side should help you find them.
LabROSA: Daniel P.W. Ellis and Thierry Bertin-Mahieux
The Echo Nest: Brian Whitman and Paul Lamere
Acknowledgements: Courtenay Cotton, Graham Grindlay, Ron Weiss, Tyler Williams
How to cite the dataset
Thierry Bertin-Mahieux, Daniel P.W. Ellis, Brian Whitman, and Paul Lamere. The Million Song Dataset. In Proceedings of the 12th International Society for Music Information Retrieval Conference (ISMIR 2011), 2011.
Use it to refer to the data, the code, and all information from this website or the github repository that is not specifically part of another publication.
Additonally, you can cite the website:
Million Song Dataset, official website by Thierry Bertin-Mahieux, available at: http://labrosa.ee.columbia.edu/millionsong/
This should not replace the publication citation.
In the press
We started keeping an informal list of blogs mentioning the dataset. First reason is pure bragging, but it's also great feedback, some point of views are quite different from ours.